I just bought a 91 Miata with a 94 engine with a DIY turbo setup. I drove the car ~600 miles home after I bought it, and the car made it without any big issues. The A/C belt has been removed and it has a SAAB inter cooler on it.
The car was originally an automatic and was converted to 5 speed. The car is running about 5-6psi boost.

I was watching the temperature gauge (It has a after market one which reads in F) while on the highway and in traffic. Even driving on the highway the gauge was hovering about 200-205 F and about the same in traffic. When I forced the A/C fan to run (Using the A/C button, the car's A/C belt has belt removed) the temperature was around 180 (both on the highway and traffic).

When I switched off the fan and switched on the inside heater the temperature was ~185-190 F.

It seem very abnormal for the car to run at 200F on the highway. The previous owner said that he had a changed the radiator to used manual transmission radiator when he swapped the transmission.